Manufacture of pneumatic tyres



Aug. 22, 1961 H. w. TREVASKIS MANUFACTURE OF PNEUMATIC TYRES 2 Sheets-Sheet 1 Filed Oct. 28, 1959 1961 H. w. TREVASKIS 2,997,095

' MANUFACTURE OF PNEUMATIC TYRES United States Patent I V 2,997,095 MANUFACTURE OF PNEUMATIC TYRES Henry William Trevaskis, Point Pleasant, Blackdown,

near Leamington Spa, England, assignor to Dunlop Rubber Company Limited, London, England, a company of Great Britain Filed Oct. 28, 1959, Ser. No. 849,200 Claims priority, application Great Britain Nov. 7, 1958 14 Claims. (Cl. 1'54---'10) This invention relates to the manufacture of pneumatic tyres. Tyres are normally built on a drum or former mounted for rotation about its central axis, which is fixed, by winding sheets of rubber and/or rubber-impregnated reinforcing material on the former. The end of each successive sheet is adhered to the former, or to a previous sheet already on it, and the former is rotated to wind the sheet round it. The sheets are normally manually or otherwise guided Whilst being wound, and are frequently drawn from a continuous bulk supply for example wound on a storage spool.

The sheets are frequently stretched or otherwise distorted by this winding and guiding so that when in position on the former they are no longer uniform. For example, in the case of reinforcing material in the form of parallel cords the spacing of the cords may become uneven due to stretching of the rubber, resulting in a nonuniform tyre.

According to the present invention a method of building pneumatic tyres from sheets of rubber and/or rubber-impregnated reinforcing material comprises the steps of supporting each sheet in substantially flat condition and rolling a building former longitudinally over it so that the sheet is picked up by and wound around the former or a sheet already wound thereon.

The sheets, when so wound on the former, can be turned down its sides either separately or in groups, and bead wires and other parts of the tyre can be applied, by any convenient method such as used in present tyr building appliances.

Further according to the invention, apparatus for building tyres comprises a support including a substantially flat surface upon which sheets can be laid and a building former mounted to roll along the support in contact with the said surface so that a sheet laidthereon may be picked up by and wound around the former as it rolls.

The support preferably includes a guide means engageable by'complementa-ry guides on the-former for controlling the direction of rolling of the former, and the substantially flat surface may be provided with locating devices or marking for facilitating the positioningof sheets thereon so as to ensure that they are picked up symmetrically by the former.

Means is preferably provided for holding the former stationary, for lifting it clear of the support, and forenabling it to be rotated whilst so lifted, to facilitate build- An embodiment of the invention is illustrated by the accompanying drawings in which:

FIGURE 1 is an elevation of apparatus for building pneumatic tyres,

FIGURE 2. is a section on the line AA of FIGURE 1, with the former shown on this line, partly in section,

FIGURE 3 is a similar view to FIGURE 1, showing part of the apparatus at a different stage of operation.

The apparatus comprises a main support in the form of a cradle 1 of length about twice the circumference of the largest tyres desired to be built, pivotally mounted on a support 2 so as to rock about its transverse centre line in see-saw fashion.

Parallel straight guide rails 3 are mounted one at each side of the top of the cradle, and between them in the middle part of the cradle is resiliently carried by floating mountings a support plate 4 having a flat upper surface parallel to the rails. The plate is mounted on bell crank levers 5 the centre pivots 6 of which are secured to the frame of the cradle, and the other ends of the levers are connected by a link 7 one end of which is connected to the cradle by a tension spring 8 by which the plate is biased upwardly towards a normal position, as shown in FIGURE 1, in which its surface is above the level of the guide rails 3. Counterweights 9 are fitted to the pivot pins of the bell crank levers to assist the action of the spring and adjustable stops (not shown) are fitted between the plate and the cradle to limit the upward movement of the plate and so fix its normal position.

The support plate is of length somewhat greater than the circumference of the largest tyres desired to be built so that a sheet for forming such a tyre can be laid on it in flat condition and will be fully supported thereby.

Between one end of the cradle and the supporting surface 10, for example a Workshop floor, on which the cradle is pivotally mounted is a pneumatic pressure operated cylinder 11 by which that end of the cradle can be raised or lowered so as to rock the cradle about its central pivot and thereby cause the guide rails to slope towards either end of the cradle as desired. In FIGURE 1 the cylinder is shown with its piston extended so that the rails slope downwardly from left to right of the figure.

A segmented building former 12 of the usual high crown shape has secured to it an axial shaft 13 and on each end of the shaft projecting from the former is a. guide wheel 14 (see FIGURE 2), of diameter equal to the maximum diameter of the former, each having a peripheral groove shaped so as to receive and roll on a guide rail of the cradle. The two guide Wheels 14 are symmetrically mounted with respect to the central plane of the former 12 and are spaced apart a distance equal to the spacing of the guide rails 3 of the cradle. The assembly of the former and guide wheels is placed in position on the cradle with the guide wheels engaging the rails so that the assembly can roll along the cradle from end to end, its direction being controlled by the guiding action of the rails engaging the grooves of the guide wheels. FIGURE 1 shows the former in position at the left hand end of the cradle, which is inclined downwardly towards the right so that the former will tend to roll down it towards the other end, the final position being shown in chain dotted lines. Conversely, if the piston is retracted into the cylinder 1 1 so as to tilt the cradle downwardly to the left the former will tend to roll from its chain-dotted position to the left hand end of the cradle again. Adjustable stops 15 are provided on upturned end parts of the cradle for engaging the wheels in the extreme positions of the former so as to prevent it rolling off the cradle.

Broadly, the operation of the apparatus is that the cradle is first tilted so that the former assembly rests against the stops 15 at the lowermost end, for example the left hand end as viewed in the drawings.

A sheet for forming a part of a carcass, for example a ply of rubberised cord fabric, is laid symmetrically along the centre line of the fiat surface of the support plate 4. Conveniently the support plate has slightly raised location ridges 16 for facilitating the symmetrical central positioning of the ply. As a further aid, when tyres are to be built from one or more sheets of steel cord fabric, magnets may be set in the surface of the support plate in positions where they will be overlain by the fabric, especially near its edges, so as to hold it in position and restrain the edges from curling. With the ply or other sheet in position, the pneumatic cylinder 11 is operated to tilt the cradle in the opposite direction into the position shown in FIGURE 1 so that the former assembly is caused to roll towards the opposite end. As the former reaches the support plate 4 it depresses and rides over it and the ply carried on it and picks up the end of the ply. If the ply is the first sheet to be wound on the drum it may be necessary for the operator, after the former has rolled over the end of the ply, to stick it to the former, but if one or more sheets are already in position on the former the end of the ply will readily adhere to those already in position. As the former continues rolling the ply is wound round and retained on it and the former comes to rest against the stops 15 at the opposite end of the cradle with the ply wound in position. The next sheet or ply for the tyre may then be laid on the support plate and the cradle can then be tilted in the opposite direction to cause the former to roll over and pick up this sheet or ply.

Since the high crown former is somewhat narrower than the plies in order to enable them to be turned down its sides, means are preferably provided for preventing the edges of the plies from turning down or creasing until the turn-down stage is reached. For this purpose a pair of hollow cylindrical side formers 17 is mounted on the former shaft, one on each side between the former and the guide wheel 14, close against the former so as to form with its crown part a substantially cylindrical building surface.

Near the left hand end of the cradle, as seen in FIG- URE 1, directly beneath the position in which the former assembly comes to rest against the stops 15 is a saddle 18 shaped to fit and support the former, mounted on two parallel pairs of links 19 pivotally mounted on the frame of the cradle. A pneumatic bellows 20 is connected between the upper pair of links and a part of the frame. When the bellows is collapsed the saddle 18 lies below the level of the rails as shown in FIGURE 1 but by expanding the bellows it can be raised above this level as shown in FIGURE 3. As shown in this figure, when the former is rolled to the left hand end of the cradle, by raising the saddle it can be lifted clear of the cradle and will be held stationary for carrying out shaping or building operations on the tyre, or for removing or placing in position the side formers 17 or other accessories. If desired, a similar saddle may be provided near the other end of the cradle.

A pair of arms 21 is pivotally mounted one at each side of the cradle also at the left hand end; Each arm is pivotally mounted on the side of the cradle and carries at its upper end a pair of rollers 22 parallel to the axis of the former. The pivots 23 of the arms are parallel to the axis of the former but offset from the vertical plane containing this axis when the former is mounted on the saddle 18, and the arms have extensions 24 shaped so that when the arms are swung over-centre the extensions will engage stops 25 on the side of the cradle to locate the arms with their rollers 22 below the shaft of the former when it is on the saddle as shown in chain-dotted lines in FIGURE 3. The arms are of length such that in this position the rollers are just clear of the shaft. Then, on lowering the saddle, the ends of the shaft will rest upon the rollers so that the whole former assembly is supported rotatably clear of the cradle and of the saddle. This enables other building or shaping operations, which require stationary rotation of the former, to be carried out. The weight of the former, acting on the arms in their over-centre position, retains them in this position. When it is desired to return the former to the cradle, the saddle is raised, the arms swung clear, and the saddle lowered.

In one process of manufacture of tyres on this apparatus, with the former initially at the lowered left-hand end of the cradle, filler strips are applied to the sides of the former and consolidated against it by annular shaping rings. A pair of turn-down guide rings is applied one to each side of the former. Each guide ring has a face sloping radially inwardly and axially towards the former, terminating in a rounded nose which engages the side of the former. An annular recess is thus formed between each guide ring and the adjacent side of the former. The previously mention'ed hollow cylindrical side formers are then fitted over the guide rings against the former so as to define a substantially cylindrical building surface.

The inner sheet of the tyre, for example a sheet of lining rubber, is laid on the surface of the support plate and located in symmetrically central position by the 10- cating ridges or other convenient means. The cradle is then tilted by actuation of the pneumatic cylinder 11 so as to cause the complete former assembly to roll towards the other end of the cradle. As the former rolls onto the end of the support plate it depresses it against the action of its counterweights and spring, and on passing over the liner the end of the liner adheres to it or is lifted and caused to do so by the operator so that the liner is picked up and wound round the former as described above. When the former comes to rest at the other end of the cradle the liner is completely in position although slight manipulation may be required on the part of the operator to ensure correct meeting of its ends. Since the former assembly is guided by the rails 3 and the wheels 14 to roll symmetrically down the cradle, and the liner is initially symmetrically placed on the support plates, the centre line of the liner is correctly wound around the centre line of the former and the liner is picked up and wound in unstretched and uniform condition. The floating mounting of the support plate, and the weights and spring urging it upwardly ensure that the liner is pressed firmly against the former throughout its length.

The second sheet, for example a ply of cord fabric, is then positioned on the support plate and the cylinder 11 actuated to tilt the cradle in the opposite direction and roll the former assembly over this ply which is picked up and wound on the former in similar manner.

The sides of the ply on the former are then turned down its sides by any convenient manner, for example the method disclosed in co-pending application of Fletcher et al. Ser. No. 788,574, filed January 23, 1959. In this method a stretched rubber ring is fitted around the ply on the central part of the former and the side former is withdrawn so as to expose the annular recess below the ply. The rubber ring is then gradually worked outwardly and contracts as it rides over the recess, so turning the plies down the side of the former into this recess.

After turning down the ply the guide rings are removed and bead wire assemblies are applied to the turned-down ply in the usual manner and the ply is turned up over the beads.

The side formers and guide rings are replaced after turning down both sides of the ply and further sheets are laid on the support plate and rolled onto the former as previously described. These further sheets may be turned down in the same manner as the first ply and the sides of the carcass so built are consolidated by profiled annular rings which are pressed against the sides of the former.

To facilitate the various operations between the winding of the successive sheets, for example the removal and fitting of the guide rings and side formers and the application of the stretched rubber ring, the former assembly is raised clear of the cradle by means of the saddle and may be rested on the arms for rotation if desired. In order to enable the side formers and guide rings-to be removed and applied, and the other elements to be applied to the sides of the former guide wheels have to be removed and afterwards replaced, the former being supported on thesaddle for these operations.

After building the carcass in the manner described the former assembly is dismantled and the former collapsed to remove the carcass which is then shaped and fitted with tread and side wall rubber by any convenient method.

By use of the invention the parts of a tyre carcass can be assembled in symmetrical relation with great accuracy and without stretching or distortion. A wellbalanced and true tyre is thus produced.

Having now described my invention, what I claim is:

1. Apparatus for the manufacture of pneumatic tyres comprising a support having a substantially fiat surface for receiving tyre building material in sheetform thereupon, said support being mounted on a pivot to rock in see-saw fashion about a central transverse pivotal axis, a tyre building former supported upon the support, said former being in contact with and free to roll along the said flat surface of the support to wrap sheets of tyre building material around the former, and means for tilting the support about its axis to cause the former to roll towards either end of the support as desired.

2. Apparatus according to claim 1 wherein the means for tilting the support is a fluid-pressure operated piston and cylinder.

3. Apparatus according to claim 1 including means for guiding the former to roll in desired directions.

4. Apparatus according to claim 3 wherein the guide means comprises a rail mounted on the support alongside the substantially flat surface and a wheel coaxially secured to the former having a peripheral groove for engaging the rail.

5. Apparatus according to claim 4 wherein a pair of rails are provided, one on each side of the said surface, and a pair of wheels for engaging them are secured one on each side of the former.

6. Apparatus according to claim 1 wherein the support comprises a flat plate on which said substantially flat surface is formed and a resilient mounting on the support for movement between a normal position above the plane along which the former rolls and a position below this plane, the mounting being such as to retain the substantially flat surface substantially parallel to the plane throughout its movement.

7. Apparatus according to claim 6 wherein the plate is mounted on swinging links pivotally mounted on the support.

8. Apparatus according to claim 7 including means for lifting the former clear of the support and holding it stationary.

9. Apparatus according to claim 8 wherein the lifting means comprises a saddle mounted on parallel swinging links pivotally connected to the support and movable to move the saddle between a normal position below the plane along which the former rolls and a raised position above that plane.

10. Apparatus according to claim 9 including means for supporting the former rotatably clear of the support.

11. Apparatus according to claim 10 wherein the means for supporting the former comprises a pair of arms pivotally mounted on the support and moveable to a position in which their ends lie below the axis of the former when it is carried on the lifting means, bearing means being provided on the ends of the arms, whereby the former is so carried, and the arms are moved to the said position, on lowering the lifting means an axial shaft of the former will engage the ends of the arms and the bearing means will support the shaft and former in freely rotable condition.

=12. Apparatus according to claim 11 wherein the bearing means at the end of each arm comprises a pair of rollers freely mounted with their axes parallel to the axis of the former and spaced apart a distance less than the diameter of the said axial shaft.

13. Apparatus according to claim 6 wherein the substantially flat surface has location means for facilitating positioning of sheets.

14. Apparatus according to claim 13, for use when tyres are to be build from one or more sheets of steel cord fabric, wherein magnets are set in the substantially flat surface for facilitating the positioning of the sheets.

References Cited in the file of this patent UNITED STATES PATENTS 1,713,927 Sheldon May 21, 1929 1,818,955 Maas Aug. 11, 1931 2,319,643 Sternard et al. May 18, 1943 

